In the technical field as mentioned above, which the present invention pertains to, excellent techniques have been developed and put in practical use by efforts of predecessors, of which the main examples are as follows.
First, Patent Document 1 has provided a continuous bulk polymerization method for obtaining a synthetic polymer component composed of styrene or derivatives thereof, and (meta)acrylic acid, (meta)acrylic acid alkyl or the other (meta)acrylic derivative, and having a low molecular weight and a sharp molecular weight distribution, by employing thermal polymerization. The method has been put in practical use.
Also, Patent Document 2 has provided a continuous bulk polymerization method for obtaining a styrene-(meta)acrylic synthetic polymer component having a low molecular weight and a sharp molecular weight distribution, although it doesn't employ thermal polymerization. The method has been put in practical use.
Furthermore, Patent Document 3 has provided a continuous bulk polymerization method for obtaining a (meta)acrylic synthetic polymer component having a low molecular weight and a sharp molecular weight distribution, although it doesn't employ thermal polymerization. The method has been put in practical use.
In addition, a continuous bulk polymerization method for a monoalkenyl derivative has been also provided (Patent Document 4). The method has been put in practical use.
Furthermore, a continuous bulk polymerization method for a copolymer mainly derived from MMA has been also provided (Patent Document 5). The method has been put in practical use.
Also, a method for producing a polystyrene having a low molecular weight by employing the combination of a vessel type of polymerization device or a pipe type of polymerization device with an extruder has been also provided (Patent Document 6).
Furthermore, a motionless mixer in which a heat carrier can pass in the last half of a reaction, and a polymerizing method using the same have been also provided (Patent Document 7).
However, these continuous bulk polymerization methods do not teach a specific process for a copolymer as intended by the present invention which contains a radically polymerizable basic monomer and a radically polymerizable acidic monomer having a carboxyl group as essential components, i.e., a continuous bulk polymerization process for an amphoteric electrolyte resin.
The utility of copolymers which contain a radically polymerizable basic monomer and a radically polymerizable acidic monomer having a carboxyl group as essential components, i.e., the utility of amphoteric electrolyte resins have been demonstrated in Patent Documents 8 and 9. Also, these Documents describe a process for producing a synthetic polymer component composed of an amphoteric electrolyte resin by a bulk polymerization method. However, these documents do not describe a process for producing a synthetic polymer components composed of an amphoteric electrolyte resin by a continuous bulk polymerization method. The bulk polymerization method for an amphoteric electrolyte resin described in these Documents in fact has a disadvantage that the production costs are high.    Patent Document 1: JP-B-02-33041    Patent Document 2: JP-B-05-61284    Patent Document 3: JP-B-05-58005    Patent Document 4: U.S. Pat. No. 3,859,268    Patent Document 5: U.S. Pat. No. 3,968,059    Patent Document 6: JP-A-2002-37804    Patent Document 7: JP-A-09-31108    Patent Document 8: JP-B-1,344,622    Patent Document 9: JP-B-1,396,151